Experiment to decode ADS-B for ground testing

[PaulvS]

Soon I will be installing ADS-B out equipment (Dynon transponder and GPS source) in my RV-6A and need to run a ground test after installation. The nearest avionics shop with a ramp test unit is 250 miles away so I've been looking for a way to run the functional test locally at my farm hangar.

I'm planning to use a Software Defined Radio receiver (SDR) similar to those used to feed flightradar24, flightaware etc to receive and decode the ADS-B signals from the transponder.

So far I've purchased and installed the USB receiver and antenna (cost under $30 USD) and can receive and display local air traffic ADS-B data using the open source ADS-B decoder "dump1090". This decoder can display most of the required data for the test but there is also additional system performance info required e.g. SIL, NAC. I'm using Excel to decode that info from the raw data.

Screen shots attached. If there is interest then I'll post an update once the transponder is installed and ground tests have been run to prove that this process will work.

 

[moosepileit]

Android's Avare ADSB Pro does this recording nicely. If you don't like Dump1090. Just need the On The Go, "OTG" function enabled on the device so the USB SDR integrates. Saves comma delineated text files.

 

[FireMedic_2009]

Not sure if you know this but take the plane up for a short flight to at least 2000 ft if you are near major airports or 3000 - 4000 ft or more if you are 100’s of miles away. Go to
https://adsbperformance.faa.gov/PAPRRequest.aspx

Fill it out and within a few minutes you’ll get a report back. It’s pretty simple. If you have no red in the report you passed.

 

[PaulvS]

Not sure if you know this but take the plane up for a short flight to at least 2000 ft if you are near major airports or 3000 - 4000 ft or more if you are 100’s of miles away. Go to
https://adsbperformance.faa.gov/PAPRRequest.aspx

Fill it out and within a few minutes you’ll get a report back. It’s pretty simple. If you have no red in the report you passed.

Thanks... plane is still under construction and is not flying yet - working on panel.
Also I'm in Aus and the FAA tool doesn't work here!

 

[Thermos]

So far I've purchased and installed the USB receiver and antenna (cost under $30 USD) and can receive and display local air traffic ADS-B data using the open source ADS-B decoder "dump1090". This decoder can display most of the required data for the test but there is also additional system performance info required e.g. SIL, NAC. I'm using Excel to decode that info from the raw data.

Hi Paul,

This is a great idea and I'd definitely like to know more when you have some info to share. Are you using dump1090 as-is to get the data you're decoding in Excel, or did you modify it?

Many thanks -

Dave

 

[PaulvS]

Dump1090

Hi Paul,

This is a great idea and I'd definitely like to know more when you have some info to share. Are you using dump1090 as-is to get the data you're decoding in Excel, or did you modify it?

Many thanks -

Dave

Hi Dave,

I'm using Dump1090 "as-is" (the Malcolm Robb fork or version from Github) with Windows 7.

The --debug switch outputs data that can be directed to a text file.
From there it's a manual process to find a type 31 (operational status) extended squitter message and copy the encoded message string to Excel for further decoding.

It would be more elegant to enhance Dump1090 to decode the relevant message types but I'm doing this as a one off "quick and dirty" to check my transponder!

PDF of the debug log file attached for interest.

Regards,
Paul.

 

[Southern Pete]

Have a look at these documents
MOD 7
MOD 14
They are from the LAA in the UK, I can't remember one describes a process for testing ABSB without a test set

 

[PaulvS]

Have a look at these documents
MOD 7
MOD 14
They are from the LAA in the UK, I can't remember one describes a process for testing ABSB without a test set

Thanks Pete, that is "most" helpful. There was a link within to a TransponderReport tool that is compatible with the SDR dongle that I have plugged in. The Royal Flying Doctor service just happened to by passing overhead and their transponder seems to be working OK! See att. for the transponder report.

Problem solved (or at least made easier) thanks to VAF and the global community!!!

 

[Thermos]

The --debug switch outputs data that can be directed to a text file.
From there it's a manual process to find a type 31 (operational status) extended squitter message and copy the encoded message string to Excel for further decoding.

It would be more elegant to enhance Dump1090 to decode the relevant message types but I'm doing this as a one off "quick and dirty" to check my transponder!

PDF of the debug log file attached for interest.

This is awesome, thanks Pete!

I've played a little with dump1090 on a Raspberry Pi, but not on Windows. I have a cheapo Win machine at the hangar for database and software updates, should be perfect for this application.

Cheers,

Dave

 

[PaulvS]

Test completed

This is just to provide an update on the outcome of the experiment; it was successful and I was able to validate that the ADS-B transponder is functioning correctly on the ground. (The aim was to conduct a ground test of a new ADS-B out Trig transponder installation to verify that it is sending out the correct data.)

The test receiver is a Software Defined Radio "SDR" USB device. There are many options on eBay but the nooelec brand has a good reputation and solid support. I bought the NESDR Mini on Amazon AU for about $45 (USD $27) including antenna and shipping.

https://www.nooelec.com/store/sdr/sdr-receivers/nesdr-mini.html

This device plugs into the USB port on a Windows PC, or a tablet, or Raspberry Pi computer.

On Windows I used DUMP1090 open source software initially to decode the ADS-B signal and display the traffic. This version worked well:

https://github.com/MalcolmRobb/dump1090

The SDR receiver and small antenna can pick up commercial traffic several hundred miles away, these signals were received through my study window.

A more complete decoder and reporter is available free from a developer in the UK:

https://getyourwings.co.uk/uncertif...st-checking-the-output-from-your-transponder/

The report that it generates includes lat, long, aircraft ID, ICAO code and the internal system indicators to validate the ADS-B out installation e.g. SIL, SDA values etc.

As a bonus, the SDR receiver when plugged into the USB port on the tablet that has Avare ADSB installed (free version on Google Play Store) and enabled for GDL90 will display direct-received traffic on Ozrunways EFB, along with other traffic that comes in via the mobile network. This provides a low cost way to display ADS-B in traffic.

There was a bit of setup work to get the receiver working initially but it was fairly straightforward and problem-free and very good "bang for the buck" and was quite interesting for the learning.

The GPS receiver was unable to receive a strong signal in the shop and I shifted the airframe to get a clear view of the sky out of the door. I also tested for interference on the radio while the transponder was functioning and there was initially some crackle due to the use of RG58 cable. I replaced this with RG400 and that resolved the interference.

 

[Snowflake]

Also I'm in Aus and the FAA tool doesn't work here!

FWIW, Canada has a similar test system you can access over the internet. Since Canada's ADS-B coverage is satellite based, and since the Aireon network is global, you may be able to use our system to test your Australian setup? No guarantees...

https://www.navcanada.ca/en/air-traffic/space-based-ads-b/public-ads-b-performance-report.aspx

 

[Canadian_JOY]

FWIW, Canada has a similar test system you can access over the internet. Since Canada's ADS-B coverage is satellite based, and since the Aireon network is global, you may be able to use our system to test your Australian setup? No guarantees...

https://www.navcanada.ca/en/air-traffic/space-based-ads-b/public-ads-b-performance-report.aspx

The NavCanada tool only provides information for flights taking place in Canadian airspace. Sometimes it doesn't even do that (I've had troubles with it finding my flights which are wholly within Canada).